The two routes are the successor to the QBx1 route, privately operated by the Queens Surface Corporation until 2005, and later operated by MTA Bus. This route ran several confusing service patterns between Co-op City and Pelham Bay, with only select runs continuing to Flushing. In September 2010, the QBx1 was split into the Bx23 and Q50 to simplify service in the Bronx, and provide full-time service between Queens and the Bronx.

North of Pelham Bay Park, the QBx1 ran several different services to different parts of Co-op City. The full route circumscribed the entire development, running (clockwise) north along the New England Thruway service road to Bartow Avenue (near the current Bay Plaza Shopping Center), through Section 1, via the Dreiser Loop, through Sections 2 and 3, via the Asch Loop in Section 4, and through Section 5 before returning to Pelham Bay. This pattern operated clockwise (sections 1-2-3-4-5) or counterclockwise (sections 5-4-3-2-1).[a] The full Flushing−Co-op City service either ran clockwise from Flushing or counterclockwise to Flushing.[2]:11, 14[9][10]

The QBx1 operated a total of ten service patterns, varying on the time of day.[2]:5 During weekday off-peak hours and weekends, the route operated either between Flushing and all five sections of Co-op City, or as a circulatory shuttle service between Pelham Bay and the five sections. During the AM peak a total of five service patterns were used. The three primary AM patterns were Pelham Bay to Bellamy Loop, serving Section 3 via sections 1-2-3; Pelham Bay to Asch Loop, serving Section 4 only; and Pelham Bay running clockwise via Bartow Avenue, serving Sections 4 and 5 before returning to Pelham Bay. The intermittent service to and from Flushing ran via the Bellamy Loop route. The three PM peak hour services were Flushing to Pelham Bay and Bellamy Loop; Pelham Bay to Bellamy Loop; and Pelham Bay running counterclockwise to Sections 5 and 4, Asch Loop, and back to Pelham Bay.[a][2]:5[9][10] While this structure provided direct service to individual sections of Co-op City, the structure was considered confusing and inconvenient due to the many different service patterns under one route designation, and the lack of service between Queens and the Bronx.[2]:5[3][10]

A now-retired Orion V bus on Q50 service near the Main Street station in Downtown Flushing

The Bx23 constitutes a simplified version of the former QBx1 route between Pelham Bay Park and Co-op City, running either clockwise (1-2-3-4-5) or counterclockwise (5-4-3-2-1) before returning to Pelham Bay.[6][11] The Q50, meanwhile, runs between Co-op City and Flushing via Pelham Bay, with its northern terminal at Erskine Place and Earhart Lane in Section 5. Q50 buses travel clockwise in Co-op City northbound, and counterclockwise southbound. The Q50 also employs limited-stop service, making fewer stops in Queens and bypassing the individual loops of Co-op City served by the Bx23.[7][12] The routes run at all times except late nights;[6][7] at these times, Co-op City service is replaced by the Bx28, while there is no direct Co-op City-to-Queens service.[13][14]

At Pelham Bay Park, both directions of Bx23 and Q50 service share three adjacent bus stops on the southbound Bruckner Boulevard to the south of the subway station. The southernmost stop at the intersection of Bruckner and Amendola Place is used by Flushing-bound Q50 service. The middle stop is used by all clockwise Co-Op City service (Q50s to Section 5 and Bx23s via 1-2-3-4-5). The northernmost stop is used by Bx23s operating the counterclockwise loop. Because of this setup, Bronx-bound Q50 buses must U-turn at Westchester Avenue to stop at Pelham Bay, then U-turn again towards Co-op City.[11][12]

Prior to 2014, the Bx23 employed additional service patterns during rush hours, similar to its predecessor route. Buses would travel via 1-2-3-4 (AM rush) or 4-3-2-1 (PM rush) and return to Pelham Bay, or directly to Section 5 via Bartow Avenue/Bay Plaza/Section 4 (clockwise AM; counterclockwise PM) and return to Pelham Bay. This was eliminated to maintain one consistent service pattern at all times, and allow service between all sections of Co-op City at all times.[2]:11–12[15]

The Bx23 and Q50 are two of the several local bus routes to serve Co-op City, which is heavily dependent on bus service. They are among five routes (along with the Bx5 on weekends, Bx12 SBS, and Bx29) to feed into Pelham Bay Park station from the neighborhood, and the only two to serve all five sections of the development (except for the late night Bx28 service).[2]:10–11[14]

Two former Queens Surface buses on the QBx1 under MTA operations before (left) and after (right) repainting into MTA colors. Both buses have since been retired.

The QBx1 was in operation since at least the mid 1960s under the Queens Transit Corporation, labeled the "Bx1" on Queens bus maps.[16] The route originally operated between Flushing and Pelham Bay Park.[17] By 1968, the QBx1 was extended to Co-op City.[18] The bus company would become Queens-Steinway Transit Corporation in 1986, and Queens Surface Corporation in 1988.[19]

On February 27, 2005, the MTA Bus Company took over the operations of the Queens Surface routes as part of the city's takeover of all the remaining privately operated bus routes.[20][21]

In 2009, ten buses from the Eastchester Depot near Co-op City (the former New York Bus Service depot) began to operate on QBx1 service.[22] Two additional stops in the Bronx were added to the route in June 2010, at Baisley Avenue (southbound) and Kearny Avenue (northbound) both at Bruckner Boulevard, to connect with a pedestrian overpass to the Country Club neighborhood.[23]

On September 12, 2010, the QBx1 was split into the Q50 Limited and Bx23 routes, simplifying the many service patterns of the former QBx1 route, but eliminating direct service between Pelham Bay and the individual sections of Co-op City.[2]:4[3][4][5] In addition, the changes were made in conjunction with controversial cuts in service to other Co-op City routes during the MTA's 2010 budget crisis,[24] and received negative input from the community.[2]:4[4][25][26]

On June 29, 2014, the rush hour service pattern of the Bx23 was eliminated, with the off-peak pattern going into effect at all times. In addition, a stop on the Bx23 was added at Adler Place in the Asch Loop. A stop for the Q50 was also added outside the Dreiser Loop.[27][28] These changes were the result of a study of bus routes in Co-op City.[2]:8[25]

In April 1994, bike racks were installed onto QBx1 buses to carry bicycles over the Whitestone Bridge. This was the first bike-on-bus program in the city.[29] The service was offered on a seasonal basis (April to September), with pick-up/drop-off points at 20th Avenue in Whitestone, Queens and Lafayette Avenue near Ferry Point Park in the Bronx.[30] However, the bike-on-bus program was eliminated on February 27, 2005, the same day as the MTA takeover.[31]

In 2017, it was announced that bike racks would be installed on the fronts of Bx23 and Q50 buses by spring 2018. Each rack, mounted on the front of each bus, would be able to carry two bicycles.[32][33] This was part of the MTA's ongoing pilot program to mount bike racks on several bus routes.[33] In September 2015, the S53 and S93 routes in Staten Island had been the first routes to receive the racks.[3][34] The expanded program restored bike racks on the Flushing to Co-op City bus corridor for the first time since 2005.[33] On July 1, 2018, bike rack service was inaugurated on the Q50 and Bx23 routes.[35]